Apparatus for treating particulate material

ABSTRACT

An apparatus for treating particulate material has a process chamber for receiving and treating the material. A bottom is composed of a plurality of overlapping guide plates which are placed one above the other and between which annular slots for process air to pass through are formed. An annular-gap nozzle is arranged centrally in the bottom, the orifice of this annular-gap nozzle being designed in such a way that a planar spray pancake which runs approximately parallel to the bottom plane can be sprayed.

FIELD OF INVENTION

This application is a continuation of pending International PatentApplication PCT/EP2004/010096 filed on Sep. 10, 2004 which designatesthe United States.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for treating particulate material,having a process chamber which is intended for receiving and treatingthe material and has a bottom which is composed of a plurality ofoverlapping guide plates which are placed one above the other andbetween which annular slots are formed, via which process air having anessentially horizontal component motion directed radially outward can beintroduced.

Such an apparatus has been disclosed, for example, by DE 102 48 116 B3.

Such known apparatuses serve to dry, granulate or coat particulatematerial. A gaseous medium, “process air”, is introduced into theprocess chamber via the bottom and enters the process chamber in anapproximately horizontally oriented manner through the numerous slotsbetween the overlapping guide plates. Due to overlapping, annular guideplates, between which numerous slots are formed, a flow of process airdirected radially from inside to outside forms in the process chamberand is deflected upward by the wall of the process chamber. The materialto be treated is entrained in the process, but falls centrally downwardon account of the gravitational force and again strikes the air cushionof the process air. If a certain extensive component is imposed on theprocess air, a toroidally revolving swirl flow ring gradually forms.

If larger agglomerates are to be formed from powders as fine as dust,that is to say if the material is to be granulated, a sticky medium issprayed toward the toroidal ring via nozzles. In DE 102 48 116 B3mentioned at the beginning, for example, spray nozzles directedobliquely upward are inserted into the wall of the container whichencloses the process chamber.

During coating, a coating layer is to be applied as uniformly aspossible to a larger body already present, that is to say said coatinglayer is to be sprayed on.

Various configurations of nozzles are known, the common feature of whichis that a usually liquid or also particulate treatment substance issprayed by means of spray air to form a fine mist. To this end, it hasbecome known, for example, to expel the liquid under high pressure froma slot-shaped nozzle orifice and to spray it through spray-air orifices,whether on one side or on both sides of the liquid gap.

DE 102 32 863 A1 has disclosed an atomizing nozzle which has flowpassages which are annular in cross section. Depending on the sprayangle and looping angle, radiate, conical or more or less planar spraypancakes are produced. At a spray angle of 180° and a looping angle of360° a virtually planar spray pancake is produced.

In this technology, which is widely used in the pharmaceutical field ofapplication, it is attempted to achieve a result which is as uniform aspossible, i.e. to achieve granulates with a very narrow grain sizedistribution, and to achieve during the coating a coating layer which isas uniform as possible, i.e. in particular a coating layer of identicalthickness, at all particles of the charge which are contained in theapparatus. A considerable problem consists in the fact that materialparticles which wander around in an uncontrolled manner and are wettedwith the moist and usually sticky spray liquid adhere to one another toform unwanted agglomerates.

Therefore precisely defined flow conditions which permit an optimumtreatment result are desired in the toroidally rotating material band.In particular, it is desired that, after the spraying, the particlesassume a flight path in which they move away from one another wherepossible and not toward one another in order to prevent undesirableagglomerates.

It is therefore the object of the present invention to provide for animprovement in such apparatuses for the treatment of particulatematerial to the effect that a harmonious sequence of movement with anoptimum treatment result can be achieved.

SUMMARY OF THE INVENTION

According to the invention, the object is achieved in that, in anapparatus of the type mentioned at the beginning, an annular-gap nozzleis arranged centrally in the bottom, the orifice of this annular-gapnozzle being designed in such a way that a planar spray pancake whichruns approximately parallel to the bottom plane can be sprayed.

The combination of such an annular-gap nozzle with a bottom of annularguide plates having a flow of process air directed from inside tooutside now leads surprisingly to an especially harmonious guidance ofair and material. The process air discharging through the annular slotsforms an air cushion which glides radially from inside to outside overthe bottom and leads the material to be treated radially outward into anincreasingly larger available space; the particles thus first of allmove away from one another.

The process air directed upward on the wall carries the materialparticles along with it vertically upward. These material particlesseparate from the process air flowing off, are moved in a radiallyinwardly directed manner toward the center and, on account of thegravitational force, fall downward approximately centrally in the centeronto the cushion of process air passing through the bottom. Due to thecentral provision of the annular-gap nozzle with the planar spraypancake sprayed from said annular-gap nozzle, the material falling downcan be sprayed uniformly and can then immediately be moved radiallyoutward in a radiated manner, that is to say the material particles canbe moved away from one another. The material particles are thereforesprayed in a very specific manner by the spray pancake when fallingdown, are cushioned by the process air cushion and are moved radiallyoutward. After leaving the spray pancake, the further path directedhorizontally radially outward, with the subsequent movement risingvertically upward and the movement returning again to the center, isavailable in order to dry and accordingly solidify the sprayed particlesby means of the process air before they strike the spray pancake again.Due to the 360° looping of the spray pancake, all the material fallingdown centrally can be sprayed uniformly by the spray liquid.

It has now been surprisingly found that a harmonious uniform optimumtreatment of the material can be achieved by this combination. Theannular-gap nozzle works “amidships” and “underbed”. The materialfalling onto the spray pancake is received by the process air cushionand is treated in an especially harmonious and uniform manner.

Even in the case of very large test batches up to 650 kg, a perfectgranulating, coating and drying process is achieved. The air cushion onthe bottom side keeps the bottom surface completely free of sprayedsubstance, i.e. all the sprayed substance is fed into the material, sothat no spray losses occur, which is extremely important in particularin the pharmaceutical field.

In a further embodiment of the invention, discharge openings for supportair are provided between theorifice of the annular-gap nozzle and thebottom lying underneath in order to effect a support cushion on theunderside of the spray pancake.

It is generally known that a certain vacuum is produced in the immediateregion of a nozzle orifice, and this vacuum results in accumulations ofmaterial next to the spray orifice. In the case of the spray pancakementioned at the beginning, no problem is to be seen on its top side inthis respect, since of course the material particles fall down centrallyand are directed away horizontally. On the underside of the spraypancake, however, such vacuum zones could gradually cause particleaccumulations. Support air is provided by the provision of theadditional discharge openings, this region on the underside in theregion of the orifice of the annular-gap nozzle being “blown free” bysaid support air. A further additional effect is that the support aircan actually support the sprayed planar spray pancake on its underside,that is to say said support air prevents the spray pancake fromundesirably moving downward on account of the gravitational force or onaccount of the spray cone forming in cross section. This rules out thepossibility of spray losses or of the sticky materials being depositedon the top side of the bottom.

In a further embodiment of the invention, the support air is providedfrom the annular-gap nozzle itself and/or by process air.

These measures enable the support air to be brought about in manydifferent ways. Discharge openings may be provided on the annular-gapnozzle itself, via which discharge openings some of the spray airdischarges in order to help to form the support air. In addition oralternatively, some of the process air which flows through the bottomcan be directed in the direction of the underside of the spray pancakeand can thus help to form the support air.

In a further embodiment of the invention, the annular-gap nozzle has anapproximately conical head, and the orifice runs along a circular areaof a conic section.

This measure has the advantage that, by means of the cone, the materialparticles moving vertically from top to bottom are fed uniformly,smoothly and specifically onto the spray pancake which is sprayed fromthe circular spray gap in the bottom end of the cone.

In a further embodiment of the invention, a frustoconical wall isprovided in the region between the orifice and the bottom lyingunderneath, this frustoconical wall having through-openings for supportair.

This measure has the advantage that the abovementioned harmoniousdeflecting movement is maintained by the continuation via the frustum,and support air can discharge through the through-openings in thisregion and provides for the corresponding support on the underside ofthe spray pancake.

In a further embodiment of the invention, an annular slot for processair to pass through is formed between the underside of the frustoconicalwall.

This measure has the advantage that the transfer of the materialparticles to the air cushion of the bottom can be controlled especiallyeffectively and, starting in a specific manner, can be carried outdirectly in the region below the nozzle.

In a further embodiment of the invention, an orifice of a feed for asubstance is arranged above the annular-gap nozzle.

It has been found that an additional substance can be fed veryeffectively on account of the harmonious flow of the selectedcombination of annular gaps and annular-gap nozzle. It is thereforepossible, for example, to directly feed a powder centrally onto thespray pancake when the latter is being formed, so that a powder can beput in a firmly adhering manner onto the surface, made sticky by thenozzle, of the material to be treated. As a result, a rapid increase inthe layer thickness during the coating can be achieved. This is not theonly advantage. A further considerable advantage consists in the factthat, for example, it is possible to feed an active substance which issensitive to moisture and therefore cannot be processed in a suspensionor in a solution and sprayed through the annular-gap nozzle. In thiscase, the annular-gap nozzle sprays only the sticky medium; the actualactive substance is fed centrally as powder. This further feeding, whichof course from the fluidic point of view is an additional parameter tobe taken into account, can therefore be carried out, since a highlydefined and harmonious flow can be achieved by the abovementionedcombination.

In a further embodiment of the invention, guide elements are arrangedbetween the annular guide plates, these guide elements additionallyimposing an extensive flow component on the process air passing through.

This measure known per se has the advantage that the correspondingextensive component motion can be imposed by these guide elements inorder to form the toroidally rotating band of uniformly swirled materialparticles, which as a result can uniformly strike the planar spraypancake.

It goes without saying that the abovementioned features and the featuresstill to be explained below can be used not only in the specifiedcombination but also in other combinations or on their own withoutdeparting from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with reference to a fewselected exemplary embodiments in connection with the attached drawings,in which:

FIG. 1 shows a highly schematic diametral cross section through anapparatus for treating particulate material, and

FIG. 2 shows a corresponding section with an additional feed for afurther substance.

DETAIL DESCRIPTION OF THE DRAWINGS

An apparatus shown in FIG. 1 for treating particulate material isprovided overall with the reference numeral 10.

The apparatus 10 has a container 12 with an upright cylindrical wall 14.This wall 14 encloses a corresponding process chamber 16.

The process chamber 16 has a bottom 18, below which an inflow chamber 20is located.

As disclosed, for example by DE 192 48 116 B3 mentioned at thebeginning, the bottom 18 is composed of a total of ten annular guideplates situated one above the other. The ten guide plates are set oneabove the other in such a way that an outermost annular plate connectedto the wall 14 forms a lowermost annular plate, on which the furthernine inner annular plates are then placed, these nine inner annularplates partly overlapping the respective annular plate underneath.

For the sake of clarity, only some of the guide plates are provided withreference numerals, for example the two guide plates 22 and 23 lying oneabove the other. By this placing one above the other and by the spacing,an annular slot 25 is formed in each case between two guide plates,through which slot 25 process air 28 having an essentially horizontallydirected component motion can pass through the bottom 18, as is ofcourse known per se. Inserted from below in the central uppermost innerguide plate 24 in its central opening is an annular-gap nozzle 30. Theannular-gap nozzle 30 has an orifice 32, which has a total of threeorifice gaps 33, 34 and 35. All three orifice gaps 33, 34 and 35 areoriented in such a way that they spray approximately parallel to thebottom 18, that is to say approximately horizontally with a loopingangle of 360°. Spray air is forced out via the top gap 33 and the lowestgap 35, and the liquid to be sprayed is forced out through the middlegap 34.

The annular-gap nozzle 30 has a rod-shaped body 36 which extendsdownward and contains the corresponding passages and feed lines, as isknown per se. The annular-gap nozzle may be designed, for example, likethe atomizing nozzle from DE 102 32 863 A1.

This annular-gap nozzle may be formed, for example, with a “rotaryannular gap”, in which the walls of the passage through which the liquidis sprayed rotate relative to one another in order to rule out cloggingor lumping, so that spraying from the gap 34 can be effected uniformlyover the entire looping angle of 360°. With respect to the longitudinalaxis of the body 36 of the annular-gap nozzle 30, there is therefore aspray angle of 180°.

The annular-gap nozzle 30 has a conical head 38 above the orifice 32.

In the region below the orifice 32, there is a frustoconical wall 40which has numerous openings 42. As can be seen from FIG. 1, theunderside of the frustoconical wall 40 rests on the innermost guideplate 24, to be precise in such a way that a slot 26 through whichprocess air can pass is formed between the underside of thefrustoconical wall 40 and the guide plate 24 lying underneath and partlyoverlapping with said wall 40.

The flow conditions which form in the run-in state are shown in theright-hand half of FIG. 1.

A planar spray pancake 44 discharges from the orifice 32. Due to the airwhich passes through the openings 42 in the frustoconical wall 40 andwhich may be, for example, process air, a support air flow 46 forms onthe underside of the spray pancake 44. Due to the process air 28 whichpasses through the numerous slots 25, 26, a radial flow forms in thedirection of the wall 14 and is deflected upward by the latter, as shownby an arrow 48. The process air and the material to be treated nowseparate from one another, the process air is drawn off through outlets,the swirled material is moved radially inward and falls verticallydownward in the direction of the conical head 38 of the annular-gapnozzle 30 on account of the gravitational force. The material fallingdown is smoothly diverted there and is directed onto the top side of thespray pancake 44 and is treated there with the sprayed medium. Thesprayed particles in the spray pancake move away from one another, sinceof course a considerably larger space is available to the particlesafter leaving the annular orifice 32. In the region of the spraypancake, the material particles to be treated collide with liquidparticles and, remaining in this direction of movement, are moved awayfrom one another and in the process are treated very uniformly andharmoniously with process air, that is to say they are dried.

A section comparable with the section in FIG. 1 is shown in perspectivein FIG. 2, the apparatus shown there being provided overall with thereference numeral 50. Here, too, there is a container 52 which has acylindrical upright wall 54 in which a process chamber 56 is defined. Asdescribed above in connection with FIG. 1, the bottom 58 is composed often guide plates correspondingly placed one above the other, only thetwo guide plates 62 and 63, for example, being designated here. Theinflow chamber 60 is then again located below the bottom 58.

It is shown here that guide elements 64 and 65 are arranged between theguide plates, these guide elements 64 and 65 leading to a situation inwhich not only does the process air passing though between the guideplates 62 and 63 flow exactly radially outward, but a certain extensivecomponent motion is imposed on said process air, as shown by the arrow68.

Here, too, a corresponding annular-gap nozzle 70 as described above isagain arranged centrally. A feed 72, for example a laterally fed pipe,is arranged centrally above the annular-gap nozzle, the orifice 74 ofthe feed 72 lying exactly coaxially centrally above the annular-gapnozzle 70. The position of the orifice can be adjusted vertically.

This makes it possible, for example, to bring a solid in the form of apowder 78 onto the top side of the planar spray pancake sprayed from theannular-gap nozzle 70.

In both configurations mentioned, the annular-gap nozzle 30 or 70,respectively, is designed in such a way that it can be removed from thebottom from below even during operation, for example in order to checkfor a malfunction or the like. Before removal, the feed of the sprayliquid is of course stopped; however, it is still possible to circulatethe material in the apparatus 10 or 50, since a process-air columnrising upward forms in the central hole, so that it is impossible formaterial particles to fall through this opening. This is again aconsequence of the highly defined harmonious swirling movement withinthe limits of the toroidally rotating band.

1. An apparatus for treating particulate material, comprising a processchamber which is intended for receiving and treating a material, saidprocess chamber having a bottom which is composed of a plurality ofoverlapping guide plates, which are placed one above the other andbetween which overlapping guide plates annular slots are formed, viawhich annular slots a process air having an essentially horizontalcomponent motion directed radially outward can be introduced into saidprocess chamber, and an annular-gap nozzle being arranged centrally insaid bottom, an orifice of said annular-gap nozzle being designed insuch a way that a planar spray pancake which runs approximately parallelto a bottom plane can be sprayed.
 2. The apparatus of claim 1, whereindischarge openings are provided between said orifice of said annular-gapnozzle and said bottom disposed underneath of said orifice, saiddischarge openings serving for discharging a support air in order toeffect a support cushion on an underside of said spray pancake.
 3. Theapparatus of claim 2, wherein said support air discharged from saiddischarge openings is provided from said annular-gap nozzle.
 4. Theapparatus of claim 2, wherein said support air discharged by saiddischarge openings is provided by said process air.
 5. The apparatus ofclaim 2, wherein said support air discharged from said dischargeopenings is provided from said annular-gap nozzle and by said processair.
 6. The apparatus of claim 1, wherein said annular-gap nozzle has anapproximately conical head, and wherein said orifice of said annular-gapnozzle runs along a circular circumferential line of said conical head.7. The apparatus of claim 6, wherein a frustoconical wall is disposedbetween said orifice of said annular-gap nozzle and said bottom lyingunderneath, said frustoconical wall having openings for discharging asupport air for supporting said planar spray pancake.
 8. The apparatusof claim 7, wherein an annular slot for passing process air is formed atan underside of said frustoconical wall.
 9. The apparatus of claim 1,wherein a feed for a substance is arranged above said annular-gapnozzle, a discharge orifice of said feed being arranged above saidannular-gap nozzle.
 10. The apparatus of claim 9, wherein said feed andthereby its discharge orifice can be adjusted vertically.
 11. Theapparatus of claim 1, wherein guide elements are arranged between saidannular guide plates, said guide elements additionally imposing a flowcomponent on said process air passing through said guide plates.